The surface properties of objects greatly influence their interaction with surrounding materials. Glass fiber reinforcement is common to articles formed from SMC in order add strength to the article. Glass fibers are routinely used that have siloxyl group rich surfaces as well as having a sizing composition imparted to the fiber strand.
Typically, an aqueous sizing composition is coated onto the fibers during fiber formation. The fibers are oven dried. During this drying process, the solids of the sizing composition have a tendency to migrate as a function of the temperatures experienced by the fibers in a spool or other large assembly. Owing to the limited nature of interaction between conventional sizing materials and a hydrophobic matrix, it is common in article failure that fibers are observed to have slide free of the matrix, with the glass fibers being generally clean of matrix material. This failure mode suggests a weak interaction between glass fibers and the matrix. This problem is complicated by non-uniform and “insufficient” sizing on the surface of the fiber that can water absorption at the non-coated fiber-resin interface leading to property degradation associated with water absorption in composites.
In the context of glass fiber reinforced matrices, the relative free energy, morphology, and chemical reactivity of a glass surface significantly affect physical and chemical properties including, but not limited to, friction, wettability, oxidation, interaction with other molecules, and so forth. SMC articles, which contain a polymeric matrix reinforced with glass fibers are used to form a variety of vehicle panels and components. For SMC materials to displace steel and aluminum in vehicle construction, it is important to provide weight savings, resistance of corrosion, and comparable strength. Water absorbed at the matrix-fiber interface can cause delamination of the substrate as the molded part goes through ovens as is required for painting and surface treatments for automotive parts.
While the prior art recognizes this problem, the solutions of re-engineering the manufacture of glass fiber has proven to be both costly and achieve performance improvements that are tied to specific types of polymer matrices.
Thus, there is a need for a surface treatment subsequent to addition of the size composition that provides load-bearing properties to a resultant article. There also exists a need to couple particle fillers to the fiber fillers to create an overall strong SMC article improve the parts performance thru paint and other treatments that require the parts to be baked at various oven temperatures.